Reinforcement laminate

ABSTRACT

A tri-laminate body panel stiffener includes two polymer layers with or without a backing. One of the layers is a compliant foam layer mounted against a substrate while the other layer is a rigid foam layer mounted against the compliant foam layer. In another aspect of the invention the laminate comprises a backing member having an expandable foam mounted thereto with two or more opposing edges of the laminate being of non-straight construction such as being wavy or saw tooth. A pattern of holes may be formed through the foam and backing layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon provisional application Serial No.60/080,014, filed Mar. 30, 1998, and provisional application Serial No.60/090,011, filed Jun. 19, 1998.

BACKGROUND OF THE INVENTION

The conventional practice to stiffen outer automotive body panels iswith a sheet thermoset polymer placed on the inside of a panel and thenheat cured in a paint oven. The conventional heat cured stiffener isapplied as a wallpaper sheet type applique or as a sprayed on layer. Theapplique is provided in a single or double layer sheet. The main layeris a thermoset layer with or without a backing. Where a backing is used,the backing can be fiberglass cloth, metal screen, or foil. The spray onis a single polymer layer without a backing. The polymer layer isgenerally 0.020 to 0.100 inches thick.

In the automotive industry when the vehicle doors are painted duringheat cure there is a problem with paint read through due to the heatcuring of the outer metal body panel stiffener and the expansion andcontraction of the metal outer panel during the paint bake cycle. Itwould be desirable if some techniques could be provided to eliminate orreduce the paint read through problem.

SUMMARY OF THE INVENTION

An object of this invention is to provide a body panel stiffener whichimproves upon the conventional practices.

A further object of this invention is to eliminate paint shadowing ormetal distortion by reducing the cure shrinkage strains during thepolymer cure and metal panel curing.

A still further object of this invention is to provide such techniqueswhich are particularly adaptable for the automotive industry.

In accordance with one aspect of this invention a laminate body panelreinforcement or stiffener is provided which includes two polymer layersmounted against a substrate with or without a backing. Preferably, oneof the polymer layers is a compliant foam which would be disposeddirectly against the substrate or structural member being reinforced. Anouter or rigid foam layer is secured to the other side of the compliantfoam layer and a carrier, such as a foil or fibreglass backing issecured to the outer surface of the rigid foam layer.

In accordance with another aspect of this invention the reinforcinglaminate for a part or substrate is made from a stiffener member orbacking having an expandable foam secured thereto. In accordance withthe invention read through is controlled by various alternativetechniques. For example, the read through can be controlled by having noparallel longitudinal edges. This can be achieved by having either wavyand/or saw tooth conditions on two and/or four opposing edges. A furthertechnique to control read through would be by the material polymerthickness and by punching or forming holes through all the polymer andbacking layers. The hole pattern can be ordered or uniform or can be ina staggered or a random display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional views in elevation of prior artstiffeners;

FIG. 3 is a cross-sectional view in elevation of a tri-laminate bodypanel stiffener in accordance with this invention;

FIG. 4 is a perspective view showing the stiffener of FIG. 3 used forautomobile door application;

FIGS. 5-7 are cross-sectional views of various configurations based onthe section A—A of FIG. 4;

FIG. 8 is a side elevational view showing the inside of a vehicle doorhaving a reinforcement laminate mounted thereto in accordance with afurther aspect of this invention;

FIG. 9 is a cross-sectional view taken through FIG. 8 along the line9—9;

FIG. 10 is a front elevational view of one form of reinforcementlaminate; and

FIG. 11 is a view similar to FIG. 10 of a modified form of reinforcementlaminate.

DETAILED DESCRIPTION

FIGS. 1-2 illustrate conventional practices for stiffening outerautomotive body panels. As shown therein a metal substrate 1 is providedon which a polymer 2 is attached. The application of the polymer 2 whichcan be a sheet thermoset polymer can be by using a wallpaper sheet typetechnique as shown in FIG. 1 or can be sprayed on as shown in FIG. 2. Inthe practice shown in FIG. 1 a fiberglass backing 3 covers the polymer2. After the polymer 2 is applied it is then heat cured in an oven.Where a wallpaper sheet type applique is used, a single or double layersheet may be applied. The main layer would be a thermoset layer with orwithout a backing. In the alternative of FIG. 2 a single polymer layeris applied without a backing. Where a backing is used the backing can befiberglass cloth, metal screen, or foil. Generally, the polymer layerwould have a thickness of 0.020 to 0.100 inches thick.

The conventional panel stiffeners such as shown in FIGS. 1 and 2 shrinkwhen they cure. Because of their good adhesion, the cure shrinkagestrains are fed into the substrate 1 to which the stiffener is bonded.Consequently, paint on the opposite face of substrate 1 would bepatterned according to the induced strains in the substrate.

FIG. 3 illustrates a stiffener 4 in accordance with this invention. Asshown therein a compliant foam layer 5 is applied directly against thepanel or metal substrate 1. A rigid foam layer 6 is applied against thecompliant foam layer 5. FIG. 3 also illustrates a foil or fiberglassbacking or carrier 7 on the outer surface of rigid foam layer 6. Thisresults in a tri-laminate body panel stiffener 4.

When the tri-laminate stiffener 4 cures the first intimate layer 5 cannot transfer shrinkage strains to the substrate 1 and layer 5 cannotrestrain the outer metal panel from shrinking when the panel comes outof the oven because it is not rigid after cure. The second layer 6 isrigid after cure but its shrinkage strain are blocked from getting tothe substrate by the compliant first layer. The backing or carrier 7 isused to provide additional stiffness.

The compliant foam layer 5 absorbs shrinkage strains due to the cure ofthe heat curable layers. Large shrinkage strains of the rigid layer 6are not fed in the metal substrate 1 but yet the rigid layer 6 with itsbacking 7 will stiffen the panel. A typical layer thicknesses are from1-1.5 mm for compliant layer 5 and 1-2.0 inches for rigid layer 6 withbacking layer 7 having a thickness of 0.002-0.004 inch. Any suitablematerials may be used for layers 5 and 6. Both polymer layers should becompatible in chemistry, however, otherwise the cured finished productof either layer will be compromised. Reference is made to my U.S. Pat.No. 5,575,526 and my application Ser. No. 09/099,025, filed Jun. 17,1998, all of the details of which the patent and application andincorporated herein by reference thereto. The patent and applicationdisclose suitable materials which may be used for the foam layer tocreate a rigid structural foam and materials for the carrier. Thespecific materials are not critical provided they function in theintended manner, namely, in that the layer 5 would be compliant whilethe layer 6 would have rigidity. Compliant layer 5 may have rubber-likecharacteristics such as materials conventionally used for refrigeratordoor seals or automobile door strips. Layer 5 may be tacky or non-tacky.

FIG. 4 illustrates the foil back laminate 4 of this invention as usedfor automobile door application. FIGS. 5-7 illustrate in cross-sectiondifferent possible configurations for such applications. As is apparentfrom FIGS. 3 and 5, the tri-polymer layer stiffener 4 may be of uniformthickness with flat planar layers as illustrated in FIG. 3.

FIG. 5, however, illustrates a door panel 1 to have a shallow curveconfiguration. The patch or stiffener 4 would conform to thatconfiguration. FIG. 5 shows the stiffener 4 to have uniform thickness.FIGS. 6-7, however, show variations which could be incorporated whichwould require non-uniform thickness. As shown, the foil backing orcarrier 7 includes an outer channel section 7A forming a rib or bead incombination with the extended portion 8 of the foam layers 5,6. The foamlayers 5,6 could be provided as two separate pairs of sheets which abutagainst each other in the channel section 7A. For example, FIG. 6 showsthe two foam layers 5 to abut each other at surface 5A. Foil backing 7may also be made of two layers which abut at the center of channel 7A.

FIG. 7 shows end extensions or flanges 7B for the foil backing 7 withconforming end flanges 9 for the pair of foam layers 5,6 in combinationwith a central extension 7C of the foil backing 7 and a centralextension 9A of the foam layers 5,6 to accommodate a rib 1A on the panel1. The provision of these outward extensions results in rib sectionsthat offer even more panel stiffening than a completely flat and/oruniform laminate because of the increase in section and redistributionof the foil backed laminate reinforcement away from the panel neutralaxis. Thus, FIGS. 6-7 illustrate the stiffener 4 to include stiffeningbeads while FIG. 7 also includes stiffening end flanges.

FIGS. 8-11 relate to another aspect of this invention which is intendedto address problems relating to paint read through which cause shadowingor metal distortion. The techniques involved in FIGS. 8-11 may be usedin combination with the tri-laminate structure of FIGS. 3-7 or may beused separately from those features.

In general, the invention illustrated in FIGS. 8-11 includes providing alaminate stiffener or reinforcement laminate for a part or substrate.The materials of the laminate and of the substrate to which it would beapplied and the uses of the invention may be those discussed withrespect to FIGS. 3-7.

As shown in FIGS. 8-9 the part or substrate 10 being reinforced is avehicle door. A reinforcement laminate 12 is mounted to the doorpreferably at generally the central area of the door. The laminate maybe of any suitable size and shape. In the preferred embodiment thelaminate is of generally rectangular shape having certain modificationswhich will be later discussed. Laminate 12 comprises a backing 14 and anintimately bonded expandable foam layer 16. Foam layer 16 may be asingle rigid structural foam layer such as in my previously noted patentand application or may be of two layer form as illustrated, for example,in FIG. 3. Layer 16 is disposed against the substrate 10. Where theinvention is used in the automotive industry FIG. 9 schematically showsa paint spray nozzle 18 applying a pattern of paint 20 to create a paintlayer 22 on the substrate 10. Where part 10 is in a paint oven in whichthe polymer 16 cures, there might be a problem with paint read throughof the heat cured outer metal panel body stiffeners. The presentinvention provides various techniques for eliminating or reducing suchpaint read through.

FIG. 10 illustrates one practice of the invention where the laminate hasa pair of longitudinal side edges 26,26 interconnected by a pair oftransverse end edges 24,24. As shown therein the opposed end edges 24,24are of non-straight linear configuration forming hills and valleys.Specifically, in the embodiment illustrated in FIG. 10 the edges 24,24are of saw tooth construction. Intermediate edges 26,26 are illustratedas being straight edges parallel to each other. It is to be understood,however, that edges 26,26 may also be of non-straight shape such ashaving sawtooth construction so that all four edges have peaks andvalleys. Alternatively, edges 26,26 may have the saw tooth constructionand edges 24,24 may be straight parallel edges.

FIG. 11 illustrates a variation wherein the longitudinal edges 28,28have peaks and valleys by being undulated or wavy. The intermediateedges 30,30 are illustrated as being straight and parallel. Theinvention, however, may be similarly practiced where edges 30,30 arealso of wavy construction similar to edges 28,28 or where the wavyconstruction is on edges 30,30, but edges 28,28 are straight andparallel.

FIG. 8 illustrates the further possibility of saw-tooth edges 24 andwavy edges 28. Thus, any arrangement of creating peaks and valleys maybe used within the broad practices of this invention including differentforms of structure to achieve the peaks and valleys along differentedges.

In accordance with a further practice of the invention read through iscontrolled by the material polymer thickness and by punching orotherwise forming holes through all of the polymer and backing layers.FIG. 10, for example, shows a pattern of holes 32 in a uniform orordered array where all of the holes are arranged in straight rows andcolumns in line with each other. FIG. 11, however, shows the holes 34 tobe in straight rows and columns which are staggered. The invention mayalso be practiced where the holes are in a random pattern, rather thanstraight rows and columns.

Where holes are provided through the laminate 12, the laminate mayoptionally include the non-straight edges such as the saw tooth and wavyformations or optionally the laminate could have some or all of theedges straight.

The invention may be practiced by forming the backing layer 14 of thedesired shape which includes the non-straight edges. The polymer orunexpanded foam may then be coated on or otherwise applied to the entiresurface of backing 14 to form the laminate 12. The laminate 12 wouldthen be mounted to substrate 10 by positioning the polymer layer 16against the substrate 10. When the polymer is activated, the foamexpands and would move backing layer 14 outwardly further away fromsubstrate 10. The foam would also expand outwardly beyond the edges ofbacking 14. The various techniques used for practicing the inventionwould result in reducing or eliminating paint shadowing or metaldistortion by reducing shrinkage strains during the polymer cure. Whilethe invention is preferably practiced with a heat expandable polymer theinvention may also be practiced with other types of expandable polymers,such as chemically activated as in the above noted application.

Although the invention has been particularly described with respect toits preferred use for reinforcing vehicle doors the concept of theinvention may be applied for reinforcing other parts. For example, theinvention may be used for roofs, deck lids and fenders of vehicles. Theinvention may also be used for reinforcing non-vehicle parts. Similarly,while the invention is preferably practiced for supporting a metalsubstrate, other substrates may be used as disclosed in the above notedapplications. The backing 14 is preferably a thin metal foil such as analuminum foil. The invention may be practiced, however, with otherbacking materials such as described in the above noted applications.

The provision of the various techniques for controlling paint throughmay be incorporated in stiffening reinforcements which include the addedfeatures of the above noted applications or which are simply part of abasic structure comprising a backing and foam laminate.

The various features described in detail herein may be used incombination with each other or separately from each other and may alsobe used in combination with the features described in my co-pendingapplication Ser. No. 09/099,025, filed on Jun. 17, 1998, pending.

What is claimed is:
 1. A reinforcement laminate for reinforcing asubstrate comprising a foil backing carrier layer, a layer of rigidreinforcement foam secured directly to said carrier layer, a layer ofcompliant foam secured directly to said rigid foam, said layer ofcompliant foam comprising a bonding layer for securing said laminate toa substrate, said rigid foam layer and said compliant foam layer beingheat curable, and said compliant foam layer comprising means forabsorbing shrinkage strains due to heat cure of said foam layer andcooling of the substrate.
 2. The laminate of claim 1 in combination withsaid substrate, and said compliant foam being intimately bonded directlyto said substrate.
 3. The laminate of claim 2 wherein said foam layersand said carrier layer have a generally continuous contour, and at leastone rib formed by said foam layers and said carrier layer forming aminor interruption of said continuous contour.
 4. The laminate of claim3 wherein said substrate includes a rib in line with said rib of saidfoam layers and said carrier layer.
 5. The laminate of claim 4 whereinsaid foam layers and said carrier layer include end flanges extending inthe same direction as each other and as said rib away from saidcontinuous contour.
 6. The laminate of claim 2 wherein said substrate isa vehicle part selected from the group consisting of a door, a roof, adeck lid and a fender.
 7. The laminate of claim 1 wherein said laminatein its elevation view has a pair of longitudinal side edgesinterconnected by a pair of transverse end edges, and at least one ofsaid pair of side edges and said pair of end edges is of non-straightand undulated shape.
 8. The laminate of claim 7 wherein said undulatedshape has a pattern of hills and valleys joined together in a smoothwavy pattern.
 9. The laminate of claim 7 wherein said undulated shapehas a pattern of hills and valleys in a sawtooth shape.
 10. The laminateof claim 7 wherein said non-straight and undulated edges are said sideedges.
 11. The laminate of claim 7 wherein said non-straight andundulated edges are said end edges.
 12. The laminate of claim 11 whereinsaid side edges are also non-straight and undulated.
 13. The laminate ofclaim 7 including a pattern of holes creating open passagewayscompletely through said laminate.
 14. The laminate of claim 13 whereinsaid pattern of holes comprises a plurality of uniformly and equallyspaced aligned rows and columns of holes.
 15. The laminate of claim 13wherein said pattern of holes comprises a plurality of holes arranged instaggered rows and columns.
 16. The laminate of claim 13 wherein saidpattern of holes is randomly arranged.
 17. The laminate of claim 7 incombination with said substrate, and said compliant foam layer beingintimately bonded to said substrate.
 18. The laminate of claim 17wherein said substrate is a vehicle door.
 19. A reinforced structurecomprising a carrier layer, a layer of rigid reinforcement foam secureddirectly to said carrier layer, a layer of compliant foam secureddirectly to said rigid foam, said layer of compliant foam comprising abonding layer for securing said laminate to a substrate, said rigid foamlayer and said compliant foam layer being heat curable, said compliantfoam layer comprising means for absorbing shrinkage strains due to heatcure of said foam layer and cooling of said substrate, said substratebeing a vehicle door, and said compliant foam layer being mounted tosaid vehicle door.
 20. The structure of claim 19 wherein said foamlayers and said carrier layer have a generally continuous contour, andat least one rib formed by said foam layers and said carrier layerforming a minor interruption of said continuous contour.
 21. Thestructure of claim 20 wherein said foam layers and said carrier layerinclude end flanges.
 22. The structure of claim 19 wherein said laminatein its elevation view has a pair of longitudinal side edgesinterconnected by a pair of transverse end edges, and at least one ofsaid pair of side edges and said pair of end edges being of non-straightand undulated shape.
 23. The structure of claim 22 including a patternof holes creating open passageways completely through said laminate.